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WATER CONSERVATION

TECHNICAL BRIEFS

TB 8 – Use of Drip Irrigation

SAI Platform

June 2010

This document has been produced for internal information purposes

only among SAI platform members. It represents a collection of

information that is freely available on the internet, and that we believe

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exhaustive document and no guarantee is provided about the content.

The views expressed herein do not reflect the official opinion of SAI

platform, nor its members.


TB 8 – Use of Drip Irrigation

WATER CONSERVATION

TECHNICAL BRIEFS

TB 8 - Use of Drip Irrigation

Adopting more efficient techniques, such as using drip irrigation systems, can help

ensure that farmers use water more efficiently. Drip irrigation systems normally

place the water directly into the soil, or onto the soil surface, reducing the risk of

runoff and thereby improving water application efficiency. Drip irrigation systems

can be classified as traditional drip irrigation system, subsurface drip irrigation and

low cost alternative systems. For a well designed, installed, and maintained

irrigation system, application efficiencies can be up to 90 % for the area irrigated.

The structure of the technical brief is as follows: Sections 1 and 2 describe drip irrigation

systems. Section 3 sets out the key issues needed to work out before the farmer decides

whether a drip irrigation system is right for a particular farm. Section 4 presents a stepby-step

decision tree for the sustainable improvement of water efficiency at a farm

level. Section 5 outlines two case studies on drip irrigation implementation in Almeria,

Spain and Greece. Section 6 outlines a set of KPI to monitor drip irrigation efficiency.

Finally, Section 7 recommends some further reading.

Contents

Section 1: What is Drip Irrigation? ...................................................................................... 2

Section 2: Drip Irrigation systems ....................................................................................... 2

Section 3: Things to consider before installing a drip irrigation system ............................ 3

Section 4: A Pathway to improve irrigation efficiency ...................................................... 5

Section 5: Case Studies ....................................................................................................... 7

Section 6: Drip Irrigation systems KPI ................................................................................. 8

Section 7: References and Further Reading ....................................................................... 9

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TB 8 – Use of Drip Irrigation

SECTION 1: WHAT IS DRIP IRRIGATION?

The use of drip irrigation enhances irrigation efficiency relative to conventional

techniques (such as gravity systems, which include flood irrigation of entire fields, and

furrow irrigation using shallow channels or ditches to carry water to the crop). With

proper management, application efficiencies for a well designed, installed, and

maintained irrigation system can be in the range of 80 to 90 % for the area irrigated.

Without proper water management, they are typically 55 to 65 %. 1 Drip irrigation can

reduce exposure to water risks and input costs making an agribusiness operation more

resilient, profitable and solvent.

SECTION 2: DRIP IRRIGATION SYSTEMS

Drip irrigation systems can be classified as traditional drip irrigation system, subsurface

drip irrigation (SDI) and low cost alternative systems.

A traditional drip irrigation system contains a

main line and sub-main lines/header (to carry

water to drip lines), laterals or drip lines (to

distribute water to the outlets at base of plants),

emitters (outlets to plants), a pump or pressure

source, a control valve (to turn system on and

off), a check valve (to prevent backflow into water

source), a fertilizer injector (to apply fertilizer

Figure 1: Drip Irrigation System Example

directly into irrigation water), a filter and a

pressure regulator. More sophisticated system can include air vents, meters, timers,

controllers and/or drains.

A subsurface drip irrigation system is similar to the system described above; however

the irrigation of crops is conducted through buried plastic tubes containing embedded

emitters located at regular spacings. This system is less vulnerable to damage during

cultivation or weeding and it is unaffected by wind. In addition, places water close to the

rooting zone (limiting evaporative loss). 2 SDI is most widely used for the irrigation of

annual row and field crops in the United States. In Israel, SDI is widely used for the

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TB 8 – Use of Drip Irrigation

irrigation of permanent crops. Subsurface drip irrigation has been used in Arizona for at

least 25 years. However, its adoption has proceeded slowly for a high initial capital and

the intensive management needed. 3

Lastly, there are low cost alternative drip

irrigation system. One of these is called

Pepsee and is used in India. It does not

require micro tubes or emitters to place

water directly to the root zone instead the

lateral. 4 However, this system has a limited

life period, cannot withstand high pressure

of flow of water and supply an unequal

distribution of water. In Rajasthan and

Gujarat, local NGOs began promoting low

cost drip irrigation among cotton growers.

Farmers saw that by using pipes and

microtubes, they can water an acre of

cotton even with this restricted pumping

Drip irrigation was invented in Israel

in 1959 as a way of using more

efficiently the scarce resource. Since

then, Israeli farmers have refined

and automated the process, linking

data on temperature, radiation,

humidity and soil-water content to

not only control where water is

released, but when, and how much

is needed to meet a plant’s need for

transpiration.

time. Drip irrigation reduces the cost of cultivation, weed problems, soil erosion and

increases water use efficiency as well as electricity use efficiency, besides helping

reduce the overexploitation of groundwater. Recent times have seen a veritable

revolution in farmers adapting drip irrigation as a survival mechanism. 5 Yet in spite of

having many economic and other advantages, the growth of area under micro-irrigation

has not so far been appreciable compared to the total potential. 6

SECTION 3: THINGS TO CONSIDER BEFORE INSTALLING A DRIP

IRRIGATION SYSTEM

The key issues needed to work out before the farmer decides whether a drip irrigation

system is right for a particular farm are:







Quantity of water used for irrigation

Irrigation efficiencies

Water quality

Crops cultivated

Topography and physical site characteristics,

Source of the water supply

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TB 8 – Use of Drip Irrigation






Energy available

Operation and management skills

Farming equipment

Environmental concerns,

Costs.

The choice of the most suitable type

of drip system depends mainly on the

soil type (light or heavy soil;

infiltration rate, lateral moisture

movement), topography (slope), crop,

water quality. Drip irrigation systems,

however, are not suitable for all crops

and soil types. Drip irrigation is well

suited to multi-season cropping such

as soft and top fruit. Where it has

been used for field scale arable row

crops or vegetables, the cost and

practical issues of pipe installation and

retrieval currently challenge its more widespread adoption.

Unilever has successfully applied drip

irrigation system in tomato, gherkin and

tea crops in different part of the World.

The use of drip irrigation in Brasilian

tomato crops has cut water use by 30%,

boosted yields and also has helped to

reduce inputs of insecticide and fungicide.

In India, a drip irrigation trial in India

produced a water saving of 40% and also

cut chemical inputs in the gherkins

cultivation. a

Water quality is an equally important consideration when determining whether a drip

irrigation system is feasible. Surface water can contain organic debris, algae, moss,

bacteria, small creatures, weed seeds, and soil particles that can clog the emitters.

Clogging is the most serious technical problem in drip irrigation systems. However,

properly designed and maintained filtration systems generally protect the system from

most clogging. In general, adequate filtration, line flushing, and chemical treatment

prevent most clogging.

In addition, not all conventional fertilisers, herbicides, fungicides, and pesticides are

compatible with drip irrigation. Farmers need to consider alternative products and/or,

preferably, integrated pest management practices.

For drip irrigation to improve water efficiency use on farms, it is crucial to provide

regular system maintenance. This will include checking visually the system and the

emitter discharge, removing and cleaning the filters and valves, checking the pressure

system and the water flow rates. An Australian study showed that more sophisticated

irrigation systems and scheduling tools do not necessarily lead to better irrigation

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TB 8 – Use of Drip Irrigation

performance. However, frequent maintenance is essential to keep drip irrigation

functioning at design flow.

SECTION 4: A PATHWAY TO IMPROVE IRRIGATION EFFICIENCY

Water application efficiency is the ratio between the water used by a crop and the total

amount of water delivered to that crop, indicating how well an irrigation system

performs in transporting water to the plant roots. A strong contrast is apparent when

comparing furrows with sprinkler and drip systems, with the former having an efficiency

of around 55 %, sprinklers 75 % and drip systems 90 % 7 .

To improve water use efficiency, farmers need to consider multiple factors, and the

importance of each will depend on the operation’s particular circumstances.

Figure 2 illustrates a step-by-step decision tree for the sustainable improvement of

water efficiency on farms. Each factor is described in more detail below.

Figure 2: Step-by-step decision tree

A. Understanding the operation´s system

Understanding the operation’s system and specific circumstances is the critical starting

point on the pathway to improving water management practices and is key to

identifying the best suited irrigation equipment. Section 3 (above) lists the key factors

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TB 8 – Use of Drip Irrigation

famers need to consider. In addition, it is also important to consider the cost of

equipment, filtration, control, and numerous laterals needed.

B. Optimise the irrigation network and equipment

To optimise the irrigation network and equipment is necessary to control pressure,

water use and uniformity. The most widespread problem is low pressure, often the

result of extending irrigation schemes without paying sufficient attention to the impacts

of increased demand on pump capacity, the distribution network and equipment

performance. The result is poor application uniformity with knock-on effects on crop

yield and quality. As discussed above, proper maintenance and regular checks are

needed on pressure and volumes of water delivered to particular fields for comparison

with manufacturer’s guidelines for pumps and in-field equipment. In-field tests using

catch-cans can be used to check that correct equipment settings (e.g. sector angle, lane

spacing etc), water pressures and flow rates are being translated into a uniform

application of water across the field.

A sustainable drip system must be reliable and able to save water, increase yields,

manage salts, allow for crop rotation, and needed tillage operations.

C. Optimising the water management practices

This hinges on ensuring that water applications are managed (scheduled) according to

crop water requirements without unnecessary waste, i.e. avoiding over-irrigation and/or

surface run-off.

Most irrigators rely on their subjective experience to determine when it is right to

irrigate, usually by walking the crop and taking soil auger samples. However, to optimise

water use efficiencies, farmers should be encouraged to adopt a mix of both subjective

and more scientific scheduling techniques.

D. Demonstrating best practice

The final step on the pathway is to demonstrate ‘best practice.’ Some of the best

practices that have proved over time to lead to more efficient irrigation are listed below.






Calculate the plant water requirements and record the evaporation rate loss to

calculate the drip systems application

Rate irrigation highly within the operation’s management system

Know the farm soils – from an irrigation perspective

Design and maintain irrigation systems correctly

Monitor all aspects of each irrigation event

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TB 8 – Use of Drip Irrigation





Use objective monitoring tools to schedule irrigation

Use more than one method to schedule irrigation

Retain control of irrigation scheduling

Remain open to new information

SECTION 5: CASE STUDIES

Case study A: Primaflor Lettuce Farm, Spain

Primaflor farm, located in Almeria, produces different varieties of lettuces. To ensure

that irrigation is undertaken in the most efficient manner, the farm has integral soil

moisture meters within the growing crop to monitor soil moisture levels. These have

sensors which monitor moisture levels over the time in order to adjust irrigation

amounts from the pre-determined target levels. Any rise in moisture levels recorded at

the shows that the crop has been over irrigated and the technician will reduce the

subsequent applications of water to address this. 8

It can be 25% more efficient than other methods of irrigation as it does not incur the

losses through evaporation that topical applications of water are subject to.

The farm has gone one step further with the introduction of a pressure compensated

drip irrigation system, which is more expensive to purchase than the convention

drippers but provides a higher degree of accuracy over the conventional system. 9

Case study B: Greece

Greece has the highest population dependent on agriculture in Europe. Between 33-

40% of total agricultural area is under irrigation, mostly for crops (approximately 70%),

vines (4%) and trees (25%). Water is often supplied through public networks. Within

these networks, efficient irrigation technologies have not been widely adopted. While

surface water irrigation accounts for 35-40% and irrigation with sprinklers amounts to

50-55%, drip irrigation remains at 10% only.

There is significant scope, therefore, to improve water productivity at the farm level by

switching to more water efficient techniques or by improving current systems. In

Greece, for example, a significant proportion of cotton is grown using flood irrigation,

which requires 20000 litres of flood water to produce a kilogram of harvested crop due

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TB 8 – Use of Drip Irrigation

to high levels of surface runoff and evaporation. Drip irrigation of cotton can require

7000 litres per kilogram of crop, although that is still seven times higher than the

volume of water needed for the production of a kilogram of wheat. 10

SECTION 6: DRIP IRRIGATION SYSTEMS KPI

Water use (m 3 /Ton): Measure the water use of all irrigated water (water

that is either taken from the mains or from the environment and directly

irrigated or stored for future uses). A recording system should be

implemented so efficiency can be measured by m 3 of water per ton of

output.

Pumped water volume (m 3 /ha): A recording system should be

implemented so water pumped can be measured by m 3 of water per ha.

Field application efficiency (%): Field application efficiency is the ratio

between the water used by a crop and the total amount of water delivered

to that crop, indicating how well an irrigation system performs in

transporting water to the plant roots.

Total length of irrigation supply channel (each of lined and unlined) (km):

A recording system should be implemented to measure the length of

irrigation pipe network in kms.

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TB 8 – Use of Drip Irrigation

SECTION 7: REFERENCES AND FURTHER READING

Best Management Guidelines for Sustainable Irrigated Agriculture

http://www.maf.govt.nz/mafnet/rural-nz/sustainable-resource-use/irrigation/irrigationbest-management/finalwater05checked.pdf

This guide offers information about technical irrigation design and management factors.

Also provides information on how to plan, to operate and review a new irrigation

system.

USDA National Irrigation Guide

http://www.saiplatform.org/site_files/uploads/documenten/#16Nationalirrigationguide

USDA(Handbook).pdf

This guide offers a comprehensive and technical guide on irrigation system.

Water management toolkit for field crop growers

http://www.ukia.org/defra.htm

The toolkit comprises a booklet and series of spreadsheets that allow farmers to

schedule their irrigation more effectively.

Waterwise on the farm

http://www.environmentagency.gov.uk/static/documents/Research/geho0307blvhepweb_432285.pdf

Water Efficiency Tool

http://www.envirowise.gov.uk/uk/Our-Services/Tools/Water-Efficiency-Tool.html

A series of modules providing guidance and call to actions for water efficiency.

Drip Irrigation Design Tutorial

http://www.irrigationtutorials.com/index.htm#sprinkler

This tutorial provides a guide to design a simple drip irrigation system for small farms.

1 www.wsi.nrcs.usda.gov/.../Irrigation/National%20Irrigation%20Guide.pdf

2 Irrigation Best Practice A Water Management Toolkit for Field Crop Growers. ww.defra.com

3 http://ag.arizona.edu/crop/irrigation/azdrip/SDI.htm

4 www.iwmi.cgiar.org/iwmi-tata_html/PM2003/PPT/.../Pepsee.ppt

5 http://www.iwmi.cgiar.org/Publications/Water_Policy_Briefs/PDF/wpb03.pdf

6 http://www.iwmi.cgiar.org/Publications/Other/PDF/Paper%2015%20of%20NRLP%20series%201.pdf

7

EEA, Water resources across Europe, Confronting Water Scarcity and droughts

http://www.eea.europa.eu/

8 http://www.flagshipfarms.eu/downloads/case_lettuce.pdf

9 http://www.flagshipfarms.eu/case5.php

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TB 8 – Use of Drip Irrigation

10 Chief Liquidity Series - Issue 1: Agribusiness (geography- and sector-specific water materiality briefings

for financial institutions) http://www.unepfi.org/fileadmin/documents/chief_liquidity1_01.pdf

10

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